/**
 * Created by 34984 on 2017/3/20.
 */
<script>
function checktree(){
    if(document.getElementById("randomCheck").checked){
        //alert("checkbox is checked");
        document.getElementById("dropMenu").style.display = "block";
    }else{
        document.getElementById("dropMenu").style.display = "none";
    }
}
</script>